Differences in the mechanism of type 1 and type 2 diabetes-induced skin dryness by using model mice

Barrier Abnormalities in Type 1 Diabetes Mellitus: The Roles of Inflammation and Ceramide Metabolism

Xerosis is a common sign of both type 1 and type 2 diabetes mellitus (DM), and patients with DM and mouse models for DM show a compromised epidermal permeability barrier. Barrier defects then allow the entry of foreign substances into the skin, triggering inflammation, infection, and worsening skin symptoms. Characterizing how barrier abnormalities develop in DM could suggest treatments for xerosis and other skin disease traits. Because the proper ratio, as well as proper bulk amounts, of heterogeneous ceramide species are keys to forming a competent barrier, we investigated how ceramide metabolism is affected in type 1 DM using a mouse model (induced by streptozotocin). Chronic inflammation, evident in the skin of mice with DM, leads to (i) decreased de novo ceramide production through serine racemase activation-mediated attenuation of serine palmitoyl transferase activity by D-serine; (ii) changes in ceramide synthase activities and expression that modify the ratio of ceramide molecular species; and (iii) increased ceramide-1-phosphate, a proinflammatory lipid mediator, that stimulates inflammatory cytokine expression (TNFα and IFN-γ). Together, chronic inflammation affects ceramide metabolism, which attenuates epidermal permeability barrier formation, and ceramide-1-phosphate could amplify this inflammation. Alleviation of chronic inflammation is a credible approach for normalizing barrier function and ameliorating diverse skin abnormalities in DM.

Skin characterization of diabetes mellitus revealed by polarization-sensitive optical coherence tomography imaging

Significance

Diabetes can lead to the glycation of proteins and dysfunction of skin collagen. Skin lesions are a prevalent clinical symptom of diabetes mellitus (DM). Early diagnosis and assessing the efficacy of treatment for DM are crucial for patient health management. However, performing a non-invasive skin assessment in the early stages of DM is challenging.

Aim

By using the polarization-sensitive optical coherent tomography (PS-OCT) imaging technique, it is possible to noninvasively assess the skin changes caused by diabetes.

Approach

The PS-OCT was used to monitor the polarization characteristics of mouse skin at different stages of diabetes.

Results

Based on a multi-layered adhesive tape model, we found that the polarization characteristics (retardation, optic axis, and polarization uniformity) were sensitive to the microstructure changes in the samples. Through this method, we observed significant changes in the polarization states of the skin as diabetes progressed. This was in line with the detected microstructure changes in skin collagen fibers using scanning electron microscopy.

Conclusions

This study presents a highly useful approach for non-invasive skin assessment of diabetes.

Cutaneous changes in diabetic patients: Primed for aberrant healing?

Cutaneous manifestations affect most patients with diabetes mellitus, clinically presenting with numerous dermatologic diseases from xerosis to diabetic foot ulcers (DFUs). Skin conditions not only impose a significantly impaired quality of life on individuals with diabetes but also predispose patients to further complications. Knowledge of cutaneous biology and the wound healing process under diabetic conditions is largely limited to animal models, and studies focusing on biology of the human condition of DFUs remain limited. In this review, we discuss the critical molecular, cellular, and structural changes to the skin in the hyperglycaemic and insulin-resistant environment of diabetes with a focus specifically on human-derived data. Elucidating the breadth of the cutaneous manifestations coupled with effective diabetes management is important for improving patient quality of life and averting future complications including wound healing disorders.

Changes in the AGE/Macrophage/TNF-α Pathway Affect Skin Dryness during KK-Ay/Tajcl Mice Aging

Skin dryness associated with type 2 diabetes worsens with age; however, the underlying mechanisms remain unclear. Herein, we investigated the effects of aging on skin dryness using a type 2 diabetes mice model. Specific pathogen-free KK-Ay/TaJcl mice of different ages (10, 27, 40, and 50 weeks) were used in this study. The results confirmed that skin dryness worsens with age. Furthermore, increased levels of advanced glycation end products (AGE), prostaglandin E2 (PGE2), and tumor necrosis factor (TNF)-α, along with an increased expression of the major AGE receptor (RAGE), an increased macrophage number, and decreased collagen expression were observed in the skin of aged KK-Ay/TaJcl mice. In conclusion, dry skin conditions worsen with age in diabetic mice, and the AGE/RAGE/PGE2 and TNF-α pathways play an important role in exacerbating skin dryness during aging in these mice.

Accumulation of Advanced Glycation End-Products in the Body and Dietary Habits

The formation of advanced glycation end-products (AGE) in tissues is a physiological process; however, excessive production and storage are pathological and lead to inflammation. A sedentary lifestyle, hypercaloric and high-fructose diet and increased intake of processed food elements contribute to excessive production of compounds, which are created in the non-enzymatic multi-stage glycation process. The AGE’s sources can be endogenous and exogenous, mainly due to processing food at high temperatures and low moisture, including grilling, roasting, and frying. Accumulation of AGE increases oxidative stress and initiates various disorders, leading to the progression of atherosclerosis, cardiovascular disease, diabetes and their complications. Inborn defensive mechanisms, recovery systems, and exogenous antioxidants (including polyphenols) protect from excessive AGE accumulation. Additionally, numerous products have anti-glycation properties, occurring mainly in fruits, vegetables, herbs, and spices. It confirms the role of diet in the prevention of civilization diseases.

Alterations in epidermal function in type 2 diabetes: Implications for the management of this disease

Epidermal function is regulated by numerous exogenous and endogenous factors, including age, psychological stress, certain skin disorders, ultraviolet irradiation and pollution, and epidermal function itself can regulate cutaneous and extracutaneous functions. The biophysical properties of the stratum corneum reflect the status of both epidermal function and systemic conditions. Type 2 diabetes in both murine models and humans displays alterations in epidermal functions, including reduced levels of stratum corneum hydration and increased epidermal permeability as well as delayed permeability barrier recovery, which can all provoke and exacerbate cutaneous inflammation. Because inflammation plays a pathogenic role in type 2 diabetes, a therapy that improves epidermal functions could be an alternative approach to mitigating type 2 diabetes and its associated cutaneous disorders.

Advanced Glycation End Products in the Skin: Molecular Mechanisms, Methods of Measurement, and Inhibitory Pathways

Advanced glycation end products (AGEs) are a series of stable compounds produced under non-enzymatic conditions by the amino groups of biomacromolecules and the free carbonyl groups of glucose or other reducing sugars commonly produced by thermally processed foods. AGEs can cause various diseases, such as diabetes, atherosclerosis, neurodegeneration, and chronic kidney disease, by triggering the receptors of AGE (RAGEs) in the human body. There is evidence that AGEs can also affect the different structures and physiological functions of the skin. However, the mechanism is complicated and cumbersome and causes various harms to the skin. This article aims to identify and summarise the formation and characteristics of AGEs, focussing on the molecular mechanisms by which AGEs affect the composition and structure of normal skin substances at different skin layers and induce skin issues. We also discuss prevention and inhibition pathways, provide a systematic and comprehensive method for measuring the content of AGEs in human skin, and summarise and analyse their advantages and disadvantages. This work can help researchers acquire a deeper understanding of the relationship between AGEs and the skin and provides a basis for the development of effective ingredients that inhibit glycation.

Skin dryness induced in the KK-Ay/TaJcl type 2 diabetes mouse model deteriorates following dapagliflozin administration

Various diabetic drugs have been developed as the number of patients with type 2 diabetes has increased. Sodium-glucose cotransporter (SGLT)-2 inhibitors have been developed as novel therapeutic agents. However, SGLT-2 inhibitors cause skin dryness. The mechanism through which SGLT-2 inhibitors cause skin dryness is unknown. The purpose of this study was to investigate the mechanism through which dapagliflozin, a SGLT-2 inhibitor, induces skin dryness. Specific pathogen-free KK-Ay/TaJcl (type 2 diabetes model) mice were orally administered with SGLT-2 inhibitor (dapagliflozin) daily for 4 weeks at a dose of 1 mg/kg/day. Skin dryness induced in KK-Ay/TaJcl mice became severe after dapagliflozin administration. Dapagliflozin treatment decreased collagen type I and hyaluronic acid levels in mice; additionally, it affected the TGF-β/hyaluronan synthase pathway, further reducing hyaluronic acid levels. The results indicate that the reduction in hyaluronic acid levels plays an important role in the occurrence of dry skin in diabetes.

Correlation of Body Mass Index with Epidermal Biophysical Properties Varies with Gender in Chinese

Background

Epidermal function is associated with diabetes and renal disease. Whether obesity can reflect the changes in epidermal function is not clear yet.

Objective

We assessed here the correlation of epidermal functions with body mass index (BMI) in a large Chinese cohort.

Methods and Subjects

A total of 1,405 Chinese aged 21–98 years old were enrolled in this study. Epidermal functions, including transepidermal water loss (TEWL), stratum corneum hydration, and skin surface pH, were measured on the flexor forearm and the shin. Subjects' height and body weight were also measured.

Results

Age positively correlated with both TEWL and skin surface pH, while it negatively correlated with stratum corneum hydration on both the forearm and the shin of females. Similarly, age positively correlated with skin surface pH, while negatively correlating with stratum corneum hydration on both the forearm and the shin of males. In females, BMI positively correlated with skin surface pH, while it negatively correlated with stratum corneum hydration on both the forearm and the shin. However, BMI correlated neither with skin surface pH on both the forearm and the shin nor with stratum corneum hydration on the shin of males.

Conclusion

These results demonstrate that correlations of BMI with age and epidermal functions vary with gender.

Diabetic Wound-Healing Science

Diabetes mellitus is an increasingly prevalent chronic metabolic disease characterized by prolonged hyperglycemia that leads to long-term health consequences. It is estimated that impaired healing of diabetic wounds affects approximately 25% of all patients with diabetes mellitus, often resulting in lower limb amputation, with subsequent high economic and psychosocial costs. The hyperglycemic environment promotes the formation of biofilms and makes diabetic wounds difficult to treat. In this review, we present updates regarding recent advances in our understanding of the pathophysiology of diabetic wounds focusing on impaired angiogenesis, neuropathy, sub-optimal chronic inflammatory response, barrier disruption, and subsequent polymicrobial infection, followed by current and future treatment strategies designed to tackle the various pathologies associated with diabetic wounds. Given the alarming increase in the prevalence of diabetes, and subsequently diabetic wounds, it is imperative that future treatment strategies target multiple causes of impaired healing in diabetic wounds.